Molecule–substrate interaction channels of metal-phthalocyanines on graphene on Ni(111) surface

Abstract

Molecule-substrate interaction channels of metal-phthalocyanines (MPcs, including NiPc, CuPc, ZnPc, FePc, and CoPc) on graphene on Ni(111) were investigated by employing high-resolution electron energy loss spectroscopy (HREELS). Except the expected IR-active modes, some Raman-active modes were also observed in all of MPcs, which are considered in this study. From the origination of the Raman-active features, it was deduced that MPcs are coupled with the substrate mainly through their central metal atom. The Raman-active modes appear as symmetric peaks in the HREELS in the case of MPcs with Ni, Cu, and Zn, whereas they are asymmetric and appear as a Fano line shape in the case of MPcs with Fe and Co. This spectroscopic difference indicates that the molecule-substrate coupling is completely different in the two cases mentioned above. The molecule-substrate interaction strength is considerably weak and comparable with the π-π interaction between molecules in the case of MPcs with Ni, Cu, and Zn, whereas it is much stronger in the case of MPcs with Fe and Co. From the HREELS observations, it can be suggested that the whole molecule can be effectively decoupled from the underneath Ni(111) by inserting a single layer of graphene between them in the case of MPcs with Ni, Cu, and Zn, whereas only benzene rings can be completely decoupled in the case of MPcs with Fe and Co.

Surface chemistry of porphyrins and phthalocyanines

“…Graphene and h-BN monolayers between the metal substrate and the adsorbed molecules can lead to a partial electronic decoupling when the metal substrate is weakly interacting, such as Ir(1 1 1) [584,628], whereas substantial residual coupling was observed for more strongly interacting substrates such as Ni(1 1 1) and Ru(0 0 0 1) [582,583,585,[598][599][600]612].…”

Effect of Interlayer Coupling on Ultrafast Charge Transfer from Semiconducting Molecules to Mono- and Bilayer Graphene

“…For comparison, previous work finds that, when FePc is deposited on graphene, ground-state charge transfer from FePc to graphene causes the Fermi level to shift up only by 0.08 eV [46]. The doping effect of ZnPc is expected to be even less due to the much weaker molecule-substrate interaction compared to that of FePc [47].…”

The electronic and transport property of the CoPc on Au(111) surface

“…Among such a family of organic semiconductor molecules, CoPc exhibits interesting electronic [12,13] and magnetic properties [11,14], such as Kondo effect which also makes it attractive in fundamental study for molecular spintronics [15]. A series of experimental and theoretical work based on (inverse) photoemission spectroscopy (PES/IPES) [16], scanning tunneling microscopy (spectroscopy) STM/STS [17], near-edge X-ray absorption fine structure (NEXAFS) [18], high-resolution electron energy loss spectroscopy (HREELS) [19] and density functional theory (DFT) simulation etc. have been carried out with CoPc as the adsorbate.…”